Chemical process



A. A. DRAEGER ETAL CHEMICAL PROCESS Filed April 8, 1942 May 23, 1944.

Patented May 23, 1944 Ferca@ Bay town. Tex., assignors to Standard OilDevelop:

ment Company,

a corporation of Delaware Application April 8, 1942, Serial No. 438,128`

12 Claims.-

This application is a continuation-impart of Serial No. 424,246, ledDecember 24, 1941.

lThe present invention relates to the treatment of hydrocarbons and, inparticular, it relates to a method for rapidly extracting oleflns from amixture of liquefied hydrocarbons containing olens with sulfuric acid.Our improved process is particularly characterized by the fact that wemay extract olens from a liquefied mixture containing the same withoutcausing degradation of said olens.

It is generally known that in a process involving the contacting ofolens with acids such as sulfuric acid and the like degradation of Vtheolefins occurs through polymerization, oxidation, condensation,sludging, and the like. In most extraction processes these undesiredside reactions are objectionable in that. of course, they result in aloss of yield of the desired final product. In the usual process forextraction of olens the olefin-containing stream is contacted with theacid in an absorption vessel of such size tlat a relatively long contactbetween the olen and the acid is unavoidable and, therefore, ex-

tensive degradation results. Upon completion of the liquid extraction,a' considerable period of time is also required for complete separationof the phases (hydrocarbon and acid). This time period required forstratification of the phases results in further degradation and, ofcourse, loss inyield. It is also known that considerable heat is evolvedin the extraction and consequently repropane, are substantiallycompletely vaprized at the mixer outlet. The pressure is controlled inorder that the acid extract will leave the mixer at the desiredtemperature. lThe niixer eflluent consists of the non-reactants (forexample, propane) in the vapor phase and the acid extract in the liquidphase. With such a mixture substantially complete separation of vaporand liquid can be obtained in -a V separation drum or the like under theconditions of short time and. hence, the extract can be rapidlyremovedfor subsequent processing to utilize the olens. In our process, weutilize the refrigeration capacity of the non-reactive componentscontained in the -heat or refrigeration in order feed; that is to say.the propane or other parafn, in that the latent heat of the vaporizationof non-reactants will absorb al1 or part of the heat liberated duringthe extraction. Depending upon the composition ofthe feed stock to theextraction zone, it may be necessary to supply external to obtain thede- Thus, for example, by dilution of the sired mixer outlet conditions.refrigeration can be supplied feed with vaporlzable non-reactants suchas frigeration must be resorted to. in order to prevent unduetemperature rises.

One object of our present process, therefore, is 'to extract olefinsfrom a mixture containing the same under such conditions that a maximumyield of the desired olellns is obtained.

Another object of our invention is to effect a separation of the desiredolens from a mixture containing the same by contacting theolefincontaining mixture for a short period of time with sulfuric acidunder conditions such that there is a minimum degradation oi the olefincontained in the feed stock..

Other and further objects of our invention will appear more fullyhereinafter.

Speaking generally at first, our invention resides in the concept ofcontacting an olefincontaining mixture, for example, a liquefied mixtureof propane and propylene, with an acid, for example, sulfonic acid, in acoil or an orifice mixer or other short time of contact mixing deviceunder temperature and pressure conditions such that the non-reactingcomponents, for example,

,n propane.

We shall now illustrate our invention by means of specific examples, itbeing understood that the precise details regarding operating conditionshereinafter set forth are merely illustrative and do not constituteEXAMPLE 1 A refinery propylene-propane fraction having the followinganalysis expressed as mol per cent was treated: Ethane, 9.4 mol percent; ethylene, 0.4fmol per cent; propylene, 21.1 mol per cent; propane68.3? mol per cent; butane, 0.8 mol per cent. This mixture was contactedwithslfuric acid having a concentration of 9098% by weight ata.temperature of -80" F., while maintaining a pressure of about, 30-40pounds per square inch gauge at the outlet of a mixer coil. In this run,98.5% of the olefin was recovered in the acid extract. v

An important use of the olens recovered according to our improved'methodis to serve as an alkylating aget for an isoparallln and, consequently,our improved method of extracting oleflns provides a more suitable olenacid extract feed for the alkylation stage of a two-'stage alkylationprocess to produce alkylates of high.,

value, and in this modification we may proceed substantially as alimitation upon our invention.

2 asians strongwsulfuric acid (oli-1009i4 bmhhand Exams: 2

21am the proilisuction ot an alkylate hav- -In order to illustrate ourinvention more coming ahighoctane number. 4More specifically. thevletely six runs were made in which prclwlene oiennfbearlng feed stockis contacted with a n# s was lbwrbed in mdb-nce with our im'ovd cycleolefin acidextract and recycled acid from mth Ind the resulting acidextract was silbthe alkylation stage in a coil, oriilce' plate mixer,seslllently aikylated with isobutane in an alhlaor other device in whichintimate contact be- Jiicn Stage. Acid strengths varying between 93.9tween hydrocarbon and acid is elected. As the a and 98% by weightsulfuric acid were employed oleilns are absorbed in the acid phase. thenonq l in a coil absorber which comprised lengths of M reactants arevaporized; The mixed hydrocarinch Dine between20 and 48 feet. Mixbonvapor acld-extract'ilows toaseparation drum ing conditions in the coliabsorber were varied where rapid separation of the two phases occurs. bychanging the pressure drops ci! the rement. The vapors are taken olfoverhead through a Apassing therethrough.A Other absorption eondi,release valve. and may be processed in any detions are those: given inthe table vwherein desired manner to obtain particular products. `'l'.hetailed data describing the runs are ses forth, extract. on the otherhand, is taken as bottoms In the alkylatlon stage the aidlexsmt im fromthe separation drum. a low liquidlevel bef the absorber was oontacte'dwith isobutane at a ing maintained in order to minimize contact time.temperature between 'I0' F.. and '15 Il. The al- A portion of theextract removed from the sepay kylation stagewas of the turbo mixer'type and ration drum is recycled to the absorption stage theacid-hydrocarbon mixture therein was main, in order to maintain thedesired hydrocarbontainedataratio of 1:1. v acid phase proportions formaximum contact eill- Yields and product inspection' data of alkyl.

ciency,andalsotocontrolthetemperatureproduced'intheseslxrunsarealsopreaentedV gradient through the mixingdevice. The reinthefollowingtable:

Table I Absorber conditions: r i

couisuznmotwpipo so so so au 4s 4a m drop through coil -..lha/sq. in-.$5 40 00 70 99 ..do..--.. 40 4o -4o 4o 4o 4o l 50 lil) 214 9d. 0 95. 0+94. 5 93. 9 94. l 1. $10 1. m 1. 4i!) l. M 1. 0:1 6:1 3:1 9:1 l. 9 2. 74. l 0. 8 9. 1 A 9i.os1.o aco aas sas Extract temperature --F- 73 70 7879 Reactor condi T en.. .r 'lnrlg Turi?) Turlisi4 -TulbToo Turb1ol'lul'hTi'ib Acidydrocarbon ratio vol.) 1:1 1:1 1:1 1:1 1:1 Spent acidtitratable ty. t HSO.. 94. 5 93. 9 .98. 4 94. 9 Yieldoitotalalkylata(baasdonomnchaxgod):

Weight, per oen 143 198 217 194 174 Volume, 108 146 166 147 182LlLP-zm'lr volumspsrosnt-- 70.0 72.5 19.2 73.1 'las 12. 7 14. d 1L 3 9.6 19. 2 H 17. 3 12. 9 9. 5 12. 3 12. 9 Gravity, A l 71. 8 70. 8 72. 211. 8 71. l E 194 196 196 195 1I B 1111111 I. B. L M F. fraction:

Gravity 75. 73. 8 74. 3 74. 9 74. 1 E M 189 189 191 1w 19! A. .T M .88.388.6 89.2 89.4 .4 Bromine num 2. 8 0. 0 0. 0 0. 4 9. 4 v

l 10% Butaue. mainder oi the acid extract containing substan- It may beseen by inspection of the data that tially all of the oleilns and all ofthe acid feed the acid extract produced in accordance with to theabsorption step is delivered to the alkylaour invention may be aikylatedto produce an altion stage in which the extract is contacted with kylatewhich is suitable for use as an aviation acid of alkylation strength andthe isoparamn gasoline or as -aviation gasoline blending agent. feed.The reacted hydrocarbon and olefin-free Furthermore, the resultsindicate that by varyacid phases from the alkylation reactor are sepingthe conditions of labsorption in the coil abarated in a settling zone,the hydrocarbon fracsoi-ber yields of alkylate (based on the oleiins)tionated to obtain the alkylate and unreacted approaching theoreticalwere attained.

isoparaiiin for recycling to the alkylation stage. In order to explainour invention more fully and the acid phase'from thesettler is returnedin reference is made to the accompanying drawing part to the alkylationstage and in part to the which shows diagrammatically a form and ar-`absorption step. The relative amounts of acid rangement oi apparatuselements in which our and oleilns charged to the absorption step are 55invention may be carried into practical eifect.

controlled in order to yield an olen acid extract Referring in detail tothe drawing, a feed stock containing vthe desired molal oleiln to acidratios containing liqueiied olens isintroduced into the for the purposeof controlling undesirable side system through line I and thence passedthrough reactions such as the formation of neutral esters, a heatexchanger 3 where it may be either heated polymers. oxidation products,and the like. We or cooled depending upon the temperature of the havefound that good results are obtained by feed stock and the amount ofrefrigeration that charging to the absorption zone a molal ratio of willbe subsequently required in vthe absorption acid to olen of from 1 to 15mois of acid per mol zone. For example, if the feed stock contains otoleiin with, however. a molal ratio ot about 3.5 1520% propylene and isavailable at a temperamols of acid per mol of olefin preferred. 7s tureof about '18 F., and a pressure of about,

' for the heat liberated during the reaction be- -tween the oleiln andthe acid. However, it will be understood that where the oleiln cotent ofthe charging stock is very low, say from to 10%,

it may be necessary to add heat'to the charging stock passing throughthe heat exchanger and, by the same token, when the relative amount ofolen is high in the charging stock, it may be necessary to extract heatin the heat exchanger I. The charging stock is withdrawn from heatexchanger 3 to line l and discharged into a mixing device consistingessentially of an orice mixer or a coil 5, thence withdrawn from saidmixer through line I0 and discharged into a separation drum I2 fromwhich drum the paraiiins and other unabsorbed material may bewithdrawn'through line I4 carrying a release valve I6. The bottoms fromdrum I2 are withdrawn through line I8. Attention is directed to the factthat a minimum amount of extract was maintained in a sump I'l at thebottom of separation drum I2 so that the average residence time of theextract in the system consisting of line 4, coil 5, line I0, separationdrum I2, line I8, pump I9, line 20, and line 60, is at a minimum. Thebottoms in line I8 are discharged into pump I9 and then recycled in partthrough lines and 60 to line I in order to control the temperatureconditions in mixer 3. "I'he remainder of the extract is discharged intoreaction vessel 22. An isoparamn is introduced into the system throughline 25, is discharged into line I8, and thereafter, together with theacid extract, is discharged into alkylation drum 22, as shown in thedrawing, and thereafter alkylated with the isoparaln under knownconditions. Reaction products are withdrawn from the alkylator throughline 35 and discharged into settling drum 30. The product is taken oifrom drum overhead through line 36. The spent acid is withdrawn fromsettling drum 30 through line 40 and recycled in part to the alkylationzone in the known manner and in part through line 45 to line 60, thenceinto line 4 for reuse in the process. Fresh acid is introduced into thesystem through line 60 to compensate for that used in the absorptionstage and the alkylation stage.

While we have illustrated our invention specically with respect, to theabsorption of olefins from a mixture containing propanes and oleflns itwill be understood that our invention also includes the separation ofany normally liquid or gaseous oleiins from a hydrocarbon mixturecontaining oleilns, parans, naphthenes, and the like. For example, thefollowing conditions have been found particularly useful in absorbingbutylenes from butylene-contalning streams:

Temperature 20 F. to 60 F. Disengaging press., Abs 8 to 40 Acid/olefinmol. ratio 0.5:1 to 1.5:1 Contact time. minutes A75 max. (preferablyExtract recycle ratio In the modification we have shown, heat exchangerl is disposed in line I.' It will be understood that it is -within thespirit of this invention to transpose heat exchanger 3 from line l toline 2l, or we may use a'second eat exchanger in line 20, 'or we may usea hea ing or a cooling medium surrounding the mixing coil 5. Manymodiilcations of our invention will suggest lthemselves to thosefamiliar with this art without departing froin the spirit thereof.

1. A process for extracting an olenic component from a mixturecontaining oleilnic and paraiiinic compon ts which comprises discharginga liquefied mixture thereof into a zone where it contacts concentratedsulfuric acid and controlling the temperature conditions prevailing inthe extraction zone, at least in part, by reducing the pressure on `theextraction zone so that at least part of the paraiilnic components isevaporated and the heat thereby absorbed compensates, at least in part,for the heat=evolved during the reaction between the acid and the`olenic components.

2. The process se't forth in claim 1 in which the residence time o theacid and the oleinic components in the extraction zone is suflicientlyshort to avoid degradation of the latter.

3. The process set forth in claim 1 in which reaction product of acidand olenic components and the unreacted material are withdrawn from thecontacting zone and discharged into a. separation zone where theunreacted portion is rapidly withdrawn in the vapor phase and theextract is withdrawn in liquid phase.

4. The process of extracting olens from a mixture of liquefiedhydrocarbons containing said olens together with paraiiins whichcomprises contacting the mixture with sulfuric acid under conditionssuch that the parailins contained in the mixture are permitted toevaporate and thereby assist in the prevention of degradation of thesaid olens by virtue of the refrigerating eiect of the evaporatingparafins.

5. The process set forth in claim 4 in which the said mixture ofhydrocarbons contains normally gaseous paralns and olens.

6. The method set forth in claim 4 in which the degradation of theoleflns is further avoided by external refrigeration.

7. The method of separating oleilns from a hydrocarbon mixturecontaining olefins and parans which comprises contacting the saidmixture in liquid lform with a sulfuric acid, adjusting pressureconditions so that during the said contact the paraffns are permitted tovaporize. and segregating the vaporized parafiins from the rest of themixture.

8. The process vset forth in claim 7 in which the parafns and olens arenormally gaseous.

9. The process set forth in claim 7 in which the parains and olens arenormally gaseous and in which external cooling means are supplied toassist in the prevention of degradation of said olens.

10. The method of separating C2, Ca, C4 olens from a mixture containingC2, C3 and C4 olenns and parafns, which comprises mixing the liquefiedC2, Ca and C4 parafilns with sulfuric acid and subjecting the mixturevto conditions such that the C2, C3 and C4 paraiiins are permitted tovaporize, thereby cooling the remainder of the mixture and substantiallypreventing degradation of said oleiins.

11. 'I'he process set forth in claim 10 in which ture thereof withnormally gaseous paramns which comprises iiquefying the mixture, mixingthe liquefied mixture with sulfuric acid of a concentration in excess of85% by weight under i2. A process for separating oleiins from amixassaut a.- pressure sumcient to keep the mixture liquid at aboutroomtemperature for a lenzth ottime denly reducing the pressure on themixture suinciently to cause vaporization of the normally gaseousparamns to thereby absorb at limit in I part the heat of solution of theolens in the acid and separating the acid extract from the vaporizedhydrocarbons. ARTHUR A. DRAEGER.

WILLIAM B. FRANKLIN.'

